1. Technical Field
The present invention relates to an oscillation circuit, an oscillator, an electronic device, and a moving object.
2. Related Art
In recent years, oscillators including a serial interface have been used. In such oscillators, a method can be used for changing an output frequency, for example, by changing the setting of a multiplication number of a phase locked loop (PLL) by operating a register within the oscillator using a signal input from a serial interface.
In such an oscillator, a terminal for a serial interface is required, but an oscillator is generally required to be small in size. For example, in the invention disclosed in JP-A-2009-201097, miniaturization is realized by making a functional terminal of an oscillator double as an inspection terminal of a quartz crystal resonator by using a switch. Here, in an embodiment of the invention disclosed in JP-A-2009-201097, the functional terminal is a standby terminal, which is a terminal having the same function as that of an output enabling terminal and having an opposite logic thereto.
However, in the invention disclosed in JP-A-2009-201097, the switch is required to be controlled when switching the dual-purpose terminal. In other words, since it is necessary to apply a signal for controlling the switch from the outside of the oscillator, a circuit or wiring for controlling the switch has to be provided, which results in problems such as redundancy in the switching process or an increase in the number of wirings for controlling the oscillator.